A Dimensionless Model for the Equilibrium Sorption of Mixtures of Acid Dyes by Polyamides from Finite Dyebaths

The equations of a dimensionless Donnan model for equilibrium sorption of ions by polymers are applied to sorption data for acid dyes in binary mixtures on nylon 66 fabric. The two acid dyes are commercial samples of C.I. Acid Blue 25 and C.I. Acid Yellow 49. Excellent fits of the data to the dimensionless model are obtained. The ratio of the distribution coefficients of the two dyes in the mixtures is estimated. Dimensionless sorption parameters have a linear dependence on the initial dye concentrations in the finite dyebaths and a linear dependence on the initial salt concentration. The equilibrium concentration distribution ratios of the two dyes on the fabric are linearly related to the ratios of their initial dyebath concentrations.